Melanie C on her Olivier nomination

Melanie Chisholm: up for an Olivier award for her role in Blood Brothers. Photograph: Andy Hall

When it is suggested to Mel Chisholm that she has done pretty well to be nominated for a Laurence Olivier award, only months into her first ever professional acting role – as Mrs Johnstone in the West End's long-running Blood Brothers, a production she joined last October – the pop star drops her chin and adopts the drawl of a career luvvie. "I think you'll find, darling, that my first professional role was in Spice Girls, the mov ie."

Back then (Spice World came out in 1997; it won no industry awards) Chisholm was at the peak of her fame as Sporty Spice, the one in the globally renowned pop quintet who had to wear football shirts but got to sing all the good bits. After the group's split, she enjoyed arguably the most successful solo career of the gang, a double- and a triple-platinum-selling album among four released between 1999 and 2007.

Recent years have been quieter. The Spice Girls are cosily reunited, surfacing for occasional gigs, and Chisholm has become a mother, giving birth to daughter Scarlet in February 2009. "I wasn't sure I'd want to work again," she says. "But Blood Brothers gives me time to be home during the day."

It is the most difficult job she has ever had – "terrifying, frustrating, a huge gamble". But Chisholm has proved a smash, wowing critics (one described the unprecedented sight of an entire row of hardened reviewers giving a standing ovation) and reinvigorating a show that has run since 1988. She is the frontrunner to win best actress in a musical at the Oliviers.

The shift to musical theatre completes a satisfying circle, begun when Chisholm was a drama graduate who auditioned for a part in Cats. It was her favourite show, and she earned a recall – but at exactly the same time, "I auditioned to be in a girl band…" Cats never saw her again.

Blood Brothers, too, will bid Chisholm goodbye when her run ends in April. All of the Spice Girls have been in to see it – to support and, perhaps, to research. A Spice Girls musical is imminent. "We're involved," she says, "giving the writers anecdotes and stuff." The hottest act in the West End, however, has no plans to audition for a role. Tom Lamont